A grand jury investigation into Home Depot’s handling of hazardous waste has expanded beyond an initial California probe to include stores nationwide, sources said. FBI agents have been contacting former Home Depot employees to question them about the company’s handling of hazardous waste, another sign that the year-old grand jury inquiry has escalated, these people continued.

Critics of Home Depot said management miscalculated the severity of the situation – which stemmed from a toxic fire at a Marina Del Rey, Calif., store in May 2004 – leaving the company vulnerable to potentially hefty fines.

Despite the ongoing investigation, Home Depot in February rolled its loss-prevention and safety departments under one umbrella, charging one person with handling everything from shoplifters to hazardous waste.

The reorganization – which caught the attention of regulators, a source said – eliminated about 150 jobs, mostly from the safety side and was seen by some insiders as yet another cost-cutting measure.

David Sandor, a Home Depot spokesman, said the company had more associates dedicated to safety than ever before. He noted that the restructuring also created a director of environmental programs in California, a new position that gives one person purview over the entire regulatory and compliance landscape.

As for the grand jury investigation, Sandor said, “We are continuing to work with respective authorities to address their environmental concerns.”

Tom Mrozek, a spokesman for the U.S. attorney’s office in L.A., which brought the case to the grand jury, declined to comment.

In an unrelated matter, Home Depot agreed to pay $425,000 earlier this month to settle allegations of environmental lapses at 13 stores in Connecticut.